I bought a used Onan 7.5KW diesel RV generator for my bus. It is a 1993 model and is open frame. It is noisier than heck and vibrates the whole bus when running. My friend and I bolted it straight to the bus.

I am thinking about replacing it with a Generac Quietpact 7.5KW gasoline unit. This unit should be much quieter and a lot less work then trying to isolate the Onan and soundproof it. I will have to add a gas tank I know.

If I only use a generator maybe 100 hours a year, is there a good reason not use a gasoline unit? Ideally, I would get a Powertech Quiet Diesel, but they cost double what the Generac costs.

Have you looked into used diesel generators? I remember when we bought ours, Dick Wright (Wrico) also had some lower $$ diesel generators which were used. He didn't always have one on hand, but it sounded like when he did, it would save money.

Only other thing I would thing of is that we really like being able to go a few days on our generator. If you are limited to a 20 gallon gasoline tank - for example, then I would project you could go about 1 1/4 days @ 3/4 gallon p/ hour. Basically the rate at which folks on this board posted for generator fuel (diesel ) consumption. If running @ 1/2 load, then maybe it would last longer. For us and our bus use, that wouldn't last long enough. However, if that was sufficient for your uses, I can't think of any other reason not to use the gasoline Onan. When we had our class A, our Onan 7.5 Marquis genset worked well for us. The only downside was that it was air cooled, and therefore, noisy. We like the quieter water cooled diesel geneator.

Have you looked into used diesel generators? I remember when we bought ours, Dick Wright (Wrico) also had some lower $$ diesel generators which were used. He didn't always have one on hand, but it sounded like when he did, it would save money.

Just to be clear I already own the 7.5KW Onan diesel. It is a water cooled 1800 RPM generator open frame. It is marked as an RV model, but it is from 1993. I would buy another used generator that had a quiet enclosure and vibration isolators in a heartbeat.

The Generac 7.5 KW gas model would be air cooled.

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Only other thing I would thing of is that we really like being able to go a few days on our generator. If you are limited to a 20 gallon gasoline tank - for example, then I would project you could go about 1 1/4 days @ 3/4 gallon p/ hour. Basically the rate at which folks on this board posted for generator fuel (diesel ) consumption. If running @ 1/2 load, then maybe it would last longer. For us and our bus use, that wouldn't last long enough. However, if that was sufficient for your uses, I can't think of any other reason not to use the gasoline Onan. When we had our class A, our Onan 7.5 Marquis genset worked well for us. The only downside was that it was air cooled, and therefore, noisy. We like the quieter water cooled diesel geneator.

I had an Onan 4KW air cooled generator in my toy hauler travel trailer and it was way quieter than my Onan diesel. Also no vibration like the Onan diesel. I am afraid the Onan diesel might literally shake the bus apart if run too long.

My 2 cents would be to call Dick @ Wrico to see whether they have a used diesel generator in house. I'm sure there are other places as well - I just know Wrico stays with you as far as help after the sale as well. I was able to call them several months later with a question / problem and they were very helpful.

If your Onan 7.5 is liquid cooled, there are lots of thing you can do to quiet it down; vibration isolators, remote radiator, sound deadening, etc. If it's air cooled, there's not much hope.

Yes, it is a liquid cooled unit. It is a real nice unit with a Kubota diesel engine, but I don't have the time to get vibration isolation and such done before I leave in a month. It shakes the bus so bad right now that I can't really use it. When we first installed it a week or two ago, we never went in the bus while it was running. I finallly ran it this weekend and went in the the bus and realized how bad it is.

If I did do a remote radiator, wouldn't I still need cooling for the generator head?

I bought a used Onan 7.5KW diesel RV generator for my bus. It is a 1993 model and is open frame. It is noisier than heck and vibrates the whole bus when running. My friend and I bolted it straight to the bus.

I am thinking about replacing it with a Generac Quietpact 7.5KW gasoline unit. This unit should be much quieter and a lot less work then trying to isolate the Onan and soundproof it. I will have to add a gas tank I know.

If I only use a generator maybe 100 hours a year, is there a good reason not use a gasoline unit? Ideally, I would get a Powertech Quiet Diesel, but they cost double what the Generac costs.

Brian Elfert

Brian,

If yours looks something like the one here, The easy part is making it quiet and basically vibration free...

If you have access to rubber mat material like is used in horse trailer flooring, 3/4 Inch thick, you can build up a set of pad strips to sit thegenerator frame on that will absorb that excess vibration. I made 2 1/2" diameter donuts of mat material and stacked them up to isolatethe genset from the floor. I welded a pair of 5 inch long 1/2 Inch bolts to the floor of the a/c bay and opened up the diameter of theholes in the genset frame. Then glued the rear pad stacks in place and put the outer ones over the bolts. Slipped the genset into thebay and then siliconed around the bolts and put another donut down over the top of the bolts and flat washer and a nut.

To silence the bay itself I used 1" A/C ductboard in the back and sides with the foil side attached to the inside of the bay walls.

I actually spaced the radiator away from the engine and used a 14" electric fan but some simple ductwork to aim the air downthrough the condenser fan hole would have worked also. That depends if the fan pushed air through the radiator or pulls it through.

If it pulls you can get a reversed plastic fan to push for the Kubota engine.

Hey guys, he does not need a diesel genset, he already has one. He just needs to bite the bullet and solve his vibration and noise problem. A 1993 unit should be a good quality unit. May be running rough or missing to cause all the vibration problem.

Buying a gasoline unit, and especially a Generac, will only adds to his problem. If it is only operated a few hours a year that is more problem as he will have fuel problems. The gasoline will go bad. Diesel will not. There is a good possibility the Generac is 3600 rpm and air cooled and lit will be worse than the Onan.

Do it right the first time and find out why you are having the problem.Richard

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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride

While I had a gasoline generator in my big rig (commercial Onan 6.5 air cooled) it was a pain in the gasoline to have to put in two different fuels, constantly changing the carb jet setting according to the altitude I was at, cleaning the sparkers, using a fan on the exhaust to push the exhaust away from the truck. I did get 12,000hrs out of it before it conked

I have a Powertech 10kw 4 cylinder Kubota with Marathon gen next to the drivers seat like a front engine. It has a remote radiator under the driver's seat with a squirrel cage belt driven fan with two speed 1/2hp motor, bathroom inline fan to push air throught the compartment. While I'd like it quieter, it is very tolerable. The standard Powertech rubber isolators work very well and when we are in the back bedroom with the A/C on watching TV, you don't even know it is on. Personally, the first thing I would do is to install the rubber isolator mounts. It sounds like the unit is bolted straight to the bus without any type of rubber isolator mounts-it's no wonder your bus vibrates so much. You'll be quite amazed at the BIG difference the rubber isolators will make. If you don't do anything else, make sure you install those isolators from Dick Wright before you leave on the trip. When you get back you can start quieting it down further. That Onan 7.5 is a good unit. Keep it, it is very easy to quiet down, and quite frankly, there aren't too many other Diesels that are as quiet as the Kubota. Good Luck, TomC

watching TV, you don't even know it is on. Personally, the first thing I would do is to install the rubber isolator mounts. It sounds like the unit is bolted straight to the bus without any type of rubber isolator mounts-it's no wonder your bus vibrates so much. You'll be quite amazed at the BIG difference the rubber isolators will make. If you don't do anything else, make sure you install those isolators from Dick Wright before you leave on the trip. When you get back you can start quieting it down further. That Onan 7.5 is a good unit. Keep it, it is very easy to quiet down, and quite frankly, there aren't too many other Diesels that are as quiet as the Kubota. Good Luck, TomC

You're correct that the generator is mounted direct to the bus. I'll probably try the homemade isolators first to see how much they help.

It looks I should forget the gasoline generator as only Generac makes a 7.5KW in a quiet model. Most recommendations are to forget about Generac.

The price for isolators and good soundproofing material looks to be around $1000 plus my time. My best bet might just be the Powertech unit that is ready to go with no additional labor except to put the genset in place. Man, I hate to spend that much, but it is a good unit by all reviews.

It looks I should forget the gasoline generator as only Generac makes a 7.5KW in a quiet model. Most recommendations are to forget about Generac.

The price for isolators and good soundproofing material looks to be around $1000 plus my time. My best bet might just be the Powertech unit that is ready to go with no additional labor except to put the genset in place. Man, I hate to spend that much, but it is a good unit by all reviews.

Brian Elfert

$1,000 ---- Duh Wow.... Mine cost all of $15.00 and $38 for a 4X8 sheet of Duct Board...) which I still have half of...Maybe my labor to mess with it was worth something, But surely not that much.

I spent more money on the 1" rubber hose to extend the radiator lines. Oh about $29 or so at Tractor Supply.Oh yeah I forgot the $69 electric fan.. duh.... ( Guys.... Rubber Horse Trailer Stall Mat is a great energy sponge...)